3a,6a,7b-Trihydroxy-5b-cholanoic acid is an unusual trihydroxy bile acid found in the urine of healthy humans, mainly in newborns (PMID 3769218 ). A bile acid. Bile acids are steroid acids found predominantly in bile of mammals. The distinction between different bile acids is minute, depends only on presence or absence of hydroxyl groups on positions 3, 7, and 12. Bile acids are physiological detergents that facilitate excretion, absorption, and transport of fats and sterols in the intestine and liver. Bile acids are also steroidal amphipathic molecules derived from the catabolism of cholesterol. They modulate bile flow and lipid secretion, are essential for the absorption of dietary fats and vitamins, and have been implicated in the regulation of all the key enzymes involved in cholesterol homeostasis. Bile acids recirculate through the liver, bile ducts, small intestine and portal vein to form an enterohepatic circuit. They exist as anions at physiological pH and, consequently, require a carrier for transport across the membranes of the enterohepatic tissues. The unique detergent properties of bile acids are essential for the digestion and intestinal absorption of hydrophobic nutrients. Bile acids have potent toxic properties (e.g., membrane disruption) and there are a plethora of mechanisms to limit their accumulation in blood and tissues. (PMID: 11316487 , 16037564 , 12576301 , 11907135 ).

This compound belongs to the class of organic compounds known as trihydroxy bile acids, alcohols and derivatives. These are prenol lipids structurally characterized by a bile acid or alcohol which bears three hydroxyl groups.

Enzymes

Ileal protein which stimulates gastric acid and pepsinogen secretion. Seems to be able to bind to bile salts and bilirubins. Isoform 2 is essential for the survival of colon cancer cells to bile acid-induced apoptosis

Mediates the Na(+)-independent transport of organic anions such as pravastatin, taurocholate, methotrexate, dehydroepiandrosterone sulfate, 17-beta-glucuronosyl estradiol, estrone sulfate, prostaglandin E2, thromboxane B2, leukotriene C3, leukotriene E4, thyroxine and triiodothyronine. May play an important role in the clearance of bile acids and organic anions from the liver

The hepatic sodium/bile acid uptake system exhibits broad substrate specificity and transports various non-bile acid organic compounds as well. It is strictly dependent on the extracellular presence of sodium.